Fix KeyCombination.IsPressed() tripping assertions when empty

[bdach]

Found this while checking something else.

After #6229, KeyCombination.IsPressed() can trip on an assertion:

System.AggregateException : One or more errors occurred. (: )
  ----> NUnit.Framework.AssertionException : :
   at osu.Framework.Testing.TestScene.checkForErrors() in /home/dachb/Documents/opensource/osu-framework/osu.Framework/Testing/TestScene.cs:line 502
   at osu.Framework.Testing.TestScene.UseTestSceneRunnerAttribute.AfterTest(ITest test) in
/home/dachb/Documents/opensource/osu-framework/osu.Framework/Testing/TestScene.cs:line 563
   at NUnit.Framework.Internal.Commands.TestActionCommand.<>c__DisplayClass0_0.<.ctor>b__1(TestExecutionContext context)
   at NUnit.Framework.Internal.Commands.BeforeAndAfterTestCommand.<>c__DisplayClass1_0.<Execute>b__1()
   at NUnit.Framework.Internal.Commands.DelegatingTestCommand.RunTestMethodInThreadAbortSafeZone(TestExecutionContext context, Action action)
--AssertionException
   at osu.Framework.Logging.ThrowingTraceListener.Fail(String message1, String message2) in
/home/dachb/Documents/opensource/osu-framework/osu.Framework/Logging/ThrowingTraceListener.cs:line 27
   at System.Diagnostics.TraceInternal.Fail(String message, String detailMessage)
   at System.Diagnostics.Debug.Fail(String message, String detailMessage)
   at osu.Framework.Input.Bindings.KeyCombination.IsPressed(ImmutableArray`1 pressedPhysicalKeys, InputKey candidateKey) in
/home/dachb/Documents/opensource/osu-framework/osu.Framework/Input/Bindings/KeyCombination.cs:line 206
   at osu.Framework.Input.Bindings.KeyCombination.IsPressed(KeyCombination pressedKeys, InputState inputState, KeyCombinationMatchingMode matchingMode) in
/home/dachb/Documents/opensource/osu-framework/osu.Framework/Input/Bindings/KeyCombination.cs:line 105
   at osu.Framework.Input.Bindings.KeyBindingContainer`1.handleNewPressed(InputState state, InputKey newKey, Nullable`1 scrollDelta, Boolean isPrecise) in
/home/dachb/Documents/opensource/osu-framework/osu.Framework/Input/Bindings/KeyBindingContainer.cs:line 227
   at osu.Framework.Input.Bindings.KeyBindingContainer`1.Handle(UIEvent e) in
/home/dachb/Documents/opensource/osu-framework/osu.Framework/Input/Bindings/KeyBindingContainer.cs:line 125
   at osu.Framework.Graphics.Drawable.OnMouseDown(MouseDownEvent e) in /home/dachb/Documents/opensource/osu-framework/osu.Framework/Graphics/Drawable.cs:line 2157
   at osu.Framework.Graphics.Drawable.TriggerEvent(UIEvent e) in /home/dachb/Documents/opensource/osu-framework/osu.Framework/Graphics/Drawable.cs:line 2033

This is happening game-side when a keybinding is vacated, at which point it is represented by KeyCombination.none or equivalent, i.e. a KeyCombination with its only key being InputKey.None.

InputKey.None is defined to be neither physical or virtual, which trips the aforementioned assertion. To bypass that entire debacle altogether, add an early return path that just returns false if the key combination being tested for being pressed is equivalent to none.

(It cannot be a reference equality check, I checked against game. Sequence equality is required. Something in game is probably instantiating anew. Probably something to do with how keybindings are materialised from realm.)

[Susko3]

The assertion that failed is still kinda wrong, but removing it also feels wrong. Probably out of scope for this PR.

diff --git a/osu.Framework/Input/Bindings/KeyCombination.cs b/osu.Framework/Input/Bindings/KeyCombination.cs
index 72c659fb3..e672119ef 100644
--- a/osu.Framework/Input/Bindings/KeyCombination.cs
+++ b/osu.Framework/Input/Bindings/KeyCombination.cs
@@ -203,8 +203,10 @@ internal static bool IsPressed(ImmutableArray<InputKey> pressedPhysicalKeys, Inp
             if (candidateKey.IsPhysical())
                 return pressedPhysicalKeys.Contains(candidateKey);
 
-            Debug.Assert(candidateKey.IsVirtual());
-            return pressedPhysicalKeys.Any(k => getVirtualKey(k) == candidateKey);
+            if (candidateKey.IsVirtual())
+                return pressedPhysicalKeys.Any(k => getVirtualKey(k) == candidateKey);
+
+            return false;
         }
 
         public bool Equals(KeyCombination other) => Keys.SequenceEqual(other.Keys);